(1) Field of the Invention
The present invention relates to the use of Pseudomonas sp. for the bioremediation of soil and/or water containing other resident microorganisms and contaminated with halogenated hydrocarbons.
(2) Description of Related Art
In particular, the present invention relates to bioaugmentation of the Pseudomonas sp in situ by the use of pH adjustment to cause suppression of the resident organisms in the soil and/or water so as to convert the halogenated hydrocarbon to carbon dioxide.
Pseudomonas have been well characterized with regard to their ability to dehalogenate various halogenated hydrocarbon compounds in nature. It has been recognized that this activity can potentially be exploited for in situ bioremediation of contaminated groundwater and soil.
Carbon tetrachloride (CT) is presently abundant as contaminant in soil and groundwater and aquifers. Carbon tetrachloride has been proven to pose health and cancer risks (Sittig, M., Ed., Handbook of Toxic and Hazardous Chemicals and Carcinogens, 2nd Ed., Noyes Pubs. N.Y. (1985)). In typical contaminated areas, chloroform is the major breakdown product of carbon tetrachloride. However, chloroform has also been associated with health and cancer risks.
Previous remediation methods utilize extraction of groundwater coupled with above-ground treatment by air stripping or adsorption to activated carbon (Nyer, E. K., Groundwater Treatment Technology, Van Nostrand Reinhold, N.Y., 35-83 (1985)). Air stripping uses large volumes of air to flush and dilute carbon tetrachloride out of water and absorption binds carbon tetrachloride to a solid material. These methods essentially transfer carbon tetrachloride from one media to another without destroying it, thereby leaving the contaminant for disposal.
Pseudomonas sp. strain KC is a denitrifying bacterium that was isolated from aquifer materials collected from Orange County Water District Well #7 of the Naval Weapons Station, Seal Beach, Calif. (Criddle et al., Appl. and Environ. Microbiol. Vol. 56, No. 11, 3240-3246 (1990)). This strain is preferred in the present invention. The publication describes the transformation of CT in sterile laboratory media. The use of the culture in various media in the laboratory is also described in Lewis and Crawford (Lewis, Thomas A. and R. L. Crawford, Applied and Environmental Microbiology, p. 1635-1641 (1993).
A xe2x80x9cnichexe2x80x9d is a term of art known to ecologists. In the present invention the environment is modified in a way that will often create a niche that can be occupied by a microorganism introduced into the environment and have the strain persist in a way that would otherwise not be possible. The microorganism can then be used to catalyze the degradation of the environmental pollutant.
It is therefore an object of the present invention to provide a method for conversion of halogenated hydrocarbons in the environment, particularly carbon tetrachloride, into carbon dioxide and water using a Pseudomonas sp. without producing toxic halogenated intermediates in the presence of other microorganisms which are suppressed. It is also an object of the present invention to provide a method wherein a portion of the environment is modified to allow the conversion by the Pseudomonas sp. to take place only in the portion. Further, it is an object of the present invention to provide a method which is simple and economical to perform. These and other objects will become increasingly apparent by reference to the following description and the drawings.